A patient monitoring system is an electronic medical device that measures a patient's various vital signs, collects and processes all measurements as data, and then displays the data graphically and/or numerically on a viewing screen. Graphical data is displayed continuously as data channels on a time axis (waveforms). Patient monitoring systems are positioned near hospital beds, typically in critical care units, where they continually monitor patient status via measuring devices attached to the patient and can be viewed by hospital personnel. Some patient monitoring systems can only be viewed on a local display, whereas others can be joined to a network and thereby display data at other locations, such as central monitoring or nurses' stations.
Portable patient monitoring systems are available for use by emergency medical services (EMS) personnel. These systems typically include a defibrillator along with the monitor. Other portable units, such as Holter monitors, are worn by patients for a particular time period and then returned to the physician for evaluation of the measured and collected data. Current patient monitoring systems are able to measure and display a variety of vital signs, including, pulse oximetry (SpO2), electrocardiograph (ECG), invasive blood pressure (IBP), non-invasive blood pressure (NIBP), electroencephalograph (EEG), body temperature, cardiac output, capnography (CO2), and respiration. Patient monitoring systems are capable of measuring and displaying maximum, minimum, and average values and frequencies, such as pulse and respiratory rates.
Data collected can be transmitted through fixed wire connections or wireless data communication. Power to patient monitoring systems can be supplied through a main power line or by batteries. While current patient monitoring systems are effective in monitoring patient conditions and notifying medical personnel of changes, they are not without certain drawbacks and limitations.
The Universal Serial Bus (USB) Interface is widely used in patient monitoring systems to connect a variety of sensors to the patient monitor. USB is a specification used to establish communication between peripheral devices and a host controller. With patient monitoring systems, the sensors are the peripheral devices and the monitor is the host controller. USB was originally designed for computers to replace serial and parallel ports and connectors, and its use has since expanded into a multitude of electronic applications. Systems using USB connections have an asymmetrical design, in which the host serves as a root hub and contains several downstream USB ports. Peripheral devices connect to the host via USB cables in a tiered star-shaped topography. Each peripheral device contains an upstream USB port. The USB cables connecting the host and peripheral devices have different connectors on the two ends. The proximal end connecting to the host has an upstream USB connector and the distal end connecting to a peripheral device has a downstream USB connector. The peripheral devices may also contain USB hubs, adding another tier to the system up to a maximum of five tiers, creating a tree-shaped topography. Peripheral devices may also draw power from the host via a USB connection. For the USB 2.0 specification, a hub can supply power in the range of 4.4 V to 5.25 V and up to 2.5 W per port. The many electronic components present in monitoring systems have varying power requirements. Some components are small with low power and/or are battery operated, and have very limited internal power capabilities. Other components require more power than what may be available from a standard USB port. Per the USB standard the device must provide the additional power itself. The power usage of the interface electronics for some devices can be a significant part of the component power.
Conventional sensor and monitor connectors are not without their drawbacks. In most legacy medical devices, each peripheral device has a unique connector controlled by a custom protocol, where the device cannot be plugged into the “wrong” connector. While some systems are moving towards USB-based cables and connectors, these connections are not without their drawbacks as well. The standard USB connection is designed to be used on a multitude of devices. Using this connector on a patient applied device could present a safety hazard if the patient applied device is connected to an inappropriate host device. Therefore, a need exists for a cable and connector interface system that incorporates the advantages of USB while eliminating the hazard mentioned above.
In addition, it is often necessary for components to receive more power than can be supplied by standard USB. Such components must then provide their own source of power at the expense of larger device size and complexity. Though power can be sent via a higher voltage auxiliary wire, the amount of this power is not unlimited. It is not uncommon for many devices to be connected to the same system, with each device competing for this limited power resource. Therefore, a need also exists for an auxiliary power system that includes a means for arbitrating and delivering power to the components so that the devices do not require individual power supplies and can thus remain small.
In the operating room and critical care units, some sensors monitoring vital signs need to be continuously connected to the patient. In such a case, patient movements are restricted due to environment conditions which may affect the sensor functionality. One such issue encountered in medical environments is liquid ingress, which can occur from a variety of sources, including but not limited to, blood splatter, liquid spill, and dropping small devices into water. This is a common scenario in many hospitals, resulting in system malfunction, time delay to restore functionality, and often damage to the system. Therefore, a need exists for a patient monitoring system in which the sensors and connectors are protected from liquid ingress.